docs: def _smcra_to_str(self, smcra, temp_dir='/tmp/'):
          """
          WHATIF's input are PDB format files.
          Converts a SMCRA object to a PDB formatted string.
          """
          
          temp_path = tempfile.mktemp( '.pdb', dir=temp_dir )
          
          io = PDBIO()
          io.set_structure(smcra)
          io.save(temp_path)
          
          f = open(temp_path, 'r')
          string = f.read()
          f.close()
          
          os.remove(temp_path)
          
          return string